1. Technical Field
The present disclosure relates to a fully differential demodulator with variable gain and to a method for demodulating a signal.
2. Description of the Related Art
As is known, demodulators find an extremely wide range of applications in numerous sectors of electronics and telecommunications. Just to provide an example, in addition to the well-known uses for transmission and reception of electromagnetic signals, demodulators are used in read chains of microelectromechanical gyroscopes. In these devices, a first movable mass is set in oscillation along an axis at a pre-determined frequency and draws in the oscillatory motion a second mass, which is constrained to the first mass so as to have one relative degree of freedom. When the gyroscope undergoes a rotation about a given axis at an angular velocity, the second mass is subjected to a Coriolis force as a result of the drawing action and moves according to the relative degree of freedom. The displacement of the second mass can be detected and transduced into electrical signals amplitude-modulated in a way proportional to the angular velocity, with a carrier at the oscillation frequency of the first mass. The use of a demodulator enables the modulating signal to be obtained and hence tracing back to the instantaneous angular velocity.
Known demodulators perform a multiplication between the modulated signal and the carrier signal in order to bring the modulating signal back into base band. They are rather complex devices that require the use of various operational amplifiers, filters and sophisticated synchronization circuits. In particular, discrete-time analog demodulators are frequently particularly complex because driving thereof requires a large number of timing signals appropriately synchronized with the carrier frequency. Consequently, not only is design difficult, but also the practical implementation can pose serious problems. For this reason, currently available demodulators, especially discrete-time analog demodulators, are not suitable for use in applications that, like microelectromechanical gyroscopes, call for extremely low levels of consumption and small overall dimensions.